As is shown in FIG. 1, control units (control devices, electronic control units, ECUs) 1201, 1202 are used in a motor vehicle 100 for controlling and/or regulating components of motor vehicle 100, such as an engine control unit 1202 for controlling and regulating a vehicle engine 110 during its operation. Control units 1201, 1202 may have up to 20,000 measured variables representing the operation and up to 20,000 parameters to be set and/or to be optimized. Control units 1201, 1202 may be connected to each other via a vehicle bus 140, such as a Controller Area Network bus (CAN bus) or FlexRay, for exchanging data between control units 1201, 1202.
During an application process, application data of a control unit 1201, 1202 are determined and set. In a simplified representation, the application process includes:                1. measuring an actual behavior, which is represented by internal variables of control unit 1201, 1202, data from other control units 1201, 1202 on vehicle bus 140, and measuring data from sensors 150 which are connected;        2. comparing the actual behavior to a setpoint behavior;        3. optimizing the application data and/or eliminating faults which are found; and        4. transmitting the optimized application data from the application process to control unit 1201, 1202 for storing the transmitted application data in control unit 1201, 1202.        
During measuring and transmission, there are generally multiple access possibilities for communicating or transmitting the data in vehicle 100:                1. via a port (interface) 1221, 1222 of control unit 1201, 1202 for vehicle bus 140, port 1221, 1222 generally also being used for a vehicle diagnosis during the development and the operation of motor vehicle 100. Advantages of vehicle bus port 1221, 1222 include a diagnostic functionality, such as erasing a fault memory and providing diagnostic services, and the elimination of additional hardware arrangement in control unit 1201, 1202 since vehicle bus port 1221, 1222 is also present during series production. Disadvantages of vehicle bus port 1221, 1222 include limited performance capability (performance) and the need for an additional interface (gateway module) 160 having a vehicle bus port 162 and a link 164 for connecting vehicle bus 140 to an external computer (such as a personal computer or laptop) 200; and        2. via a special emulator probe (ETK) 300 having a link 304, which is able to read data from a memory of the control circuit or of control unit 1201, 1202 and/or write data into the memory, such as via a debug interface of a control circuit (controller) of control unit 1201, 1202. Emulator probe 300 is connected to application tool 210 via a further interface for this purpose. Advantages of emulator probe 300 include a high performance capability when transmitting data and/or accessing the memory. According to the related art, both access types are required for the application process. To this end, vehicle bus 140, which often times is accessible only with difficulty, must be disconnected for measuring. If vehicle bus 140 is to be available on a diagnostic connector, an additional link, such as line 142, and an additional interface 160, which generally requires a dedicated power supply, must be provided—in every motor vehicle 100. The disadvantage is thus in particular the complexity for the wiring and/or additional hardware arrangement.        
When updating (flashing) a (control) program of a control unit 1202 via emulator probe 300, a driving function must be deactivated for principle-related reasons and/or for safety reasons. Since control unit 1202 to be updated does not transmit any data via vehicle bus 140, the other control units are aware of the absence of the data and switch, as intended, into a fault operating mode. However, to end the fault operating mode, a defined communication via vehicle bus port 1221, 1222 is required. The disadvantage is thus that generally both access types are required for updating a control unit 1202.